The present invention relates to an improved process for the pyrolysis of carbonous materials, such as coal, to produce liquid and gaseous products, by the use of iron and/or zinc soluble salts prior to pyrolysis.
Coal, once the leading source of energy in the United States, is beginning to play a more important role in the nation's energy future. The primary reason for the growing importance of coal is the rapid depletion of known petroleum and natural gas reserves. These known reserves are being depleted at a rate considerably faster than the rate of discovering new reserves. As the era of petroleum growth draws to a close, the world's commercial energy mix will have to change. Transition energy sources will be needed as a bridge between petroleum and the potentially unlimited energy sources of the future; such sources being, for example, solar power and nuclear fusion. Owing to their great abundance, coal and oil shale are perceived as the keystones of such a bridge. Consequently, much work is presently in progress to provide economical ways of converting these resources to valuable liquid and gaseous products. Coal liquefaction and pyrolysis processes in which coal, with or without a diluent, is subjected to elevated temperatures and pressures to convert solid coal to normally liquid hydrocarbonaceous products, are well known.
Pyrolysis of coal to yield liquids and char is an area of technology which has the potential of leading the way to a successful national synfuels program. The major limitations of present coal pyrolysis technology are the low quality of simple pyrolysis liquids combined with high sulfur content. Even when a coal in relatively low sulfur content is employed to reduce the need for hydrotreating, the product is generally low in yield and has stability problems.
By the practice of the present invention, pyrolysis in the presence of hydrogen is advantageously combined under certain conditions, to give increased yields and more stable liquid products than those acquired by use of pyrolysis processes conventionally known.